1. Field of the Invention
The present invention relates to an ink reservoir of an ink jet printer for supplying ink to a nozzle portion jetting the ink and, more particularly, to an ink reservoir of an ink jet printer comprising a mechanism for opening and closing an outlet feeding the ink.
2. Description of the Related Art
An ink jet printer drawing a letter or a diagram on paper by jetting ink in th state of particles and controlling its direction is already well-known. Especially, an an ink on demand system which jets ink particles at need has been developed recently, its range for application is wide spread. For example, a fundamental description of the ink jet printer is given, focusing on the trends of development of an ink gun of the ink on demand type ink jet printer, in "NIKKEI ELECTRONICS", Oct. 3, 1977, pp. 72.about.85.
Referring to FIGs. 1 to 4, a description is given of a whole structure of a conventional ink jet printer in general.
FIG. 1 is a plan view showing a whole structure of a conventional ink jet printer and FIG. 2 is a sectional view taken along a line A--A in FIG. 1. Referring to FIGS. 1 and 2, slide shafts 2 and 3 are disposed on a parallel with the axis of a cylindrical platen 1 and have both ends fixed to a frame 4. A carriage 6 equipped with an ink tank 5 is supported movably in a horizontal direction along the platen 1 by slide shafts 2 and 3. A wire extended around a drum 8 and pulleys 9 and 10 connected to the rotary shaft of a motor 7 is attached to the carriage 6. The carriage 6 moves back and forth within a writing region on the right side from a home position 5A by the rotation of the motor 7 during printing and is positioned at the home position 5A when not printing (in waiting).
A printing head portion 12 is disposed ahead of the carriage 5 so as to be opposed to the platen 1. Nozzles 13 each gradually changed in height are disposed, as shown in FIG. 3, on the printing head portion 12. A mechanism for jetting ink from this nozzle 13 is enlarged and shown in FIG. 4. Operation of the ink jet from the nozzle 13 is as follows. That is, the nozzle 13 is filled with ink through a capillary 14 by a capillary phenomenon. The ink in this nozzle is jetted from a nozzle outlet 17 to the outside by pressure applied to a pressure chamber 16162 the pumping operation of a piezoelectric element 15.
An opening/closing means 19 for opening/closing an ink outlet feeding ink 18, in the ink tank 5, to the capillary 14 is provided at the front of the ink tank 5 see the left portion in FIG. 2). The opening/closing means 19 comprises an ink outlet 20 formed on the bottom portion of the ink tank 5, an opening/closing lid 21 made of rubber for opening/closing the ink outlet 20, an operating rod 22 protruded from the lid 21 upward in the ink tank 5, a bellows-type expansion sleeve 23 covering around the operating rod 22, a compression coil spring 24 attached at the upper edge of the operating rod 22; and a spring bearing member 25 receiving the compression coil spring 24. The end of the operating arm 27 extended from a maintenance station 26 is placed on the upper portion of the spring bearing member 25. The operating arm 27 is vertically about a supporting point 30 by the vertical movement of a cam follower 29 following the rotation of an eccentric cam 28. When the end of this opening arm 27 falls to push the upper surface of the spring bearing member 25, the opening/closing lid 21 falls against the force of the compression spring 24 to open/close the ink inlet 20. When the downward force of the operating arm 27 is relieved, the opening/closing lid 21 is raised by the force of th compression spring 24 to open the ink inlet 20.
In addition, the maintenance station 26 comprises nozzle protecting means 31 for preventing the nozzle 13 from becoming clogged up, which is forced in a direction away from the printing head 12 by an extension spring 32. This nozzle protecting means 31 can be moved horizontally together with the rotation of the eccentric cam 33 and abuts on the printing head portion 12, which waits at the home position 5A, to prevent clogging such as suction due to a reduced pressure at the outlet portion 17 of the nozzle 13 when the ink printer power is off. An apparatus for preventing the nozzle from clogging up is disclosed in detail in Japanese Paten Laid-Open No. 185451/1986 (corresponding to U.S. Pat. No. 4,734,718).
The nozzle protecting means 31 is mutually interlocked withthe operating arm 27 because the eccentric cams 28 and 33 are integrally rotated about the same axis. More specifically, when the ink jet printer power is off and the printing head portion 12 waits at the home position 5A, the nozzle protecting means 31 abuts on the printing head portion at the same time the end of the operating lever 27 pushes the spring bearing member 25, causing the opening/closing lid 21 to close the ink outlet 20. In addition, when the ink jet printer power is on, the opening/closing lid 21 is raised at the same time the nozzle protecting means 31 goes away from the printing head portion 12, to open the ink outlet 20. FIG. 2 shows the state just after the printing head portion 12 reaches the home position 5A. Therefore, the state of the ink tank 5 is the same as that of printing, that is, both ink outlet 20 and vent hole 34 provided on the upper portion of the ink tank 5 are opened. The vent hole is opened during printing in order to prevent bubbles from entering into the nozzle 13 such that the pressure in the ink tank 5 may not become negative even if the ink jet is jetted from the nozzle 13.
When the ink jet printer power is off, the outlet opening/closing means 19 is in the state shown in FIG. 5, that is, the state in which the opening/closing lid 21 closes the ink outlet 20 and the vent hole 34 equipped with the cap 35 which closes it. In this manner, the ink is prevented from leaking during transportation by closing the vent hole 34 at the time the power is off. An ink inlet 36 is provided on the upper portion of the ink tank 5 other than the vent hole 34. This ink inlet 36 is provided for supplying ink to the ink tank 5 by attaching an ink cartride (not shown) to this and the ink is prevented from escaping out of the ink inlet 36 by closing the ink inlet 36 with the cap 37 except for the time when ink is supplied.
The ink reservoir comprising the ink tank 5 and the outlet opening/closing means 19 of the above-described conventional ink jet printer as its main part has the following disadvantages.
In the above conventional ink reservoir, since the closing operation of the vent hole 36 is performed using the cap 35 by hand, the vent hole 34 is sometimes left opening during transportation and ink leaks out of the ink inlet to contaminate around and interrupts the operation of the other mechanisms.
Contrarily, there is a case where the printing operation is performed after transportation with the vent holes 34 closed with the cap 35, causing a pressure inside of the ink tank to be reduced and air to enter from the nozzle 13, with the result that ink is not smoothly supplied.
In addition, an ink supplying apparatus of an ink jet printer having the same fundamental structure as the above is disclosed in Japanese Patent Laid Open Gazette No. 188154/1986. The apparatus in that disclosure comprises a mechanism for preventing human error in handling a transportation cap closing the ink inlet when the ink jet printer is transported. However, in this conventional technique, means for preventing failure of the opening/closing operation of the vent hole is not disclosed.